Friday, December 31, 2010

Lake Eyre to flood.

The Australian Bureau of Meteorology is reporting that flooding is occurring across Australia’s Queenland. The rivers that drain into the inland Lake Eyre are experiencing flooding, the rivers include; Thomson, Barcoo, and Cooper creeks.


Minor flooding is easing in the Thomson River at Camoola Park, with rises and moderate flooding occurring downstream at Longreach. Minor to moderate flooding is rising downstream between Stonehenge and Jundah.


Moderate flooding continues in the Alice River at Barcaldine. Minor flooding is easing in the upper Barcoo River at Blackall. River rises and major flooding is occurring along the lower Barcoo River between Coolagh and Oma where levels should peak in the next few days. Moderate to major flooding continues between Wahroongha and Retreat, with further rises expected into next week. At 9am Thursday, the river level at Retreat was 6.48 metres, which is about 4.3 metres above the Barcoo River Causeway.

COOPER CREEK:Youtube documentary

Moderate flooding is rising in the Cooper Creek at Windorah with a return to major flood levels expected in the next few days. At 3pm Thursday the creek level was 4.84 metres, which was about 0.54 metres above the level of the approaches to the Diamantina Development Road. Moderate flooding is easing downstream at Durham Downs however renewed rises and moderate flooding is expected later next week as upstream floodwaters from the Windorah area arrive.

The Lake Eyre Basin (LEB) is an unregulated system, with streamflows in the Basin being highly
variable (Puckridge et al., 1998; Knighton and Nanson, 2001). During large flood events, the LEB
rivers transform from a string of waterholes into slow moving, “inland seas” that can be as much as 60 km wide in their mid to lower reaches. Floods in these rivers are generated from rain in the upper reaches and can take months to travel to terminal wetlands or the ultimate Basin terminus of Lake Eyre North. The rivers and creeks in the region are intermittent to ephemeral, and only flow following rain periods.

Many reaches of the LEB rivers have complex flow paths with extensive
anastomosing channel systems (that is the channels bifurcate, branch and then rejoin irregularly) with greatly varying widths of active channel and floodplain. During large flood events, floodwaters can inundate thousands of square kilometres. Within the anastomosing channel system there is a complex array of waterholes, wetlands, channels and floodplains, which result in only a very small proportion of the regional rainfall arriving at Lake Eyre.

The rivers of the LEB have high ecological value and are amongst the last of the unregulated large rivers in Australia. The rivers are the foci for spectacular booms and busts in animal populations. During large flood events they support large populations of fish (Puckridge et al., 2000) and waterbirds (Kingsford, 1995; Kingsford et al., 1999) with population numbers crashing as flow ceases and surface water contracts back to the more persistent waterholes and wetlands.

Although cattle grazing, tourism and, locally, natural gas production, have had some impact on the landscape, the catchments supplying Lake Eyre are considered to be in minimally disturbed
condition. The LEB is considered significant as a result of the unusual features of the area, which
include (Morton et al., 1995):

Lake Eyre, the terminus of the Basin, is located in north-east South Australia. The lake is the fifth largest terminal lake in the world, consisting of two sections: Lake Eyre North and Lake Eyre South. The total surface area of the lake is approximately 9,690 km2, supporting a volume of 30.1 km3 (3.01x104 GL) at -9.5 AHD (see Figure 2-1; International Lake Environment Committee, undated). Originally, it was believed by European settlers that Lake Eyre North was permanently dry, however this was disproved in 1949, the first scientifically recorded filling of the lake. Since this time, numerous inflow events into Lake Eyre have been recorded, including a significant filling event that lasted several years in the mid 1970s.

Lake Eyre South is known to have filled in 1938, 1955, 1963, 1968, 1973, 1974, 1975, 1976 and
1984. In 1984 Lake Eyre South overflowed to Lake Eyre North (Hutton, 1984). In 1974 water
flowed from Lake Eyre North to Lake Eyre South between March and October when an
equilibrium level was obtained. Groyder Channel is a 15km channel that links Lake Eyre North and South. The width and bottom elevation of the channel change with each significant event.
Lake Eyre itself supports a range of flora and fauna, including emerged and submerged
macrophytes, zooplankton, algae and fish.


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